This disclosure relates to a radio-frequency amplifier circuit in which a plurality of amplifiers are cascode-connected to each other and also to a control voltage setting method for the radio-frequency amplifier circuit.
Hitherto, for increasing the gain of amplifier circuits, various radio-frequency amplifier circuits have been provided in which a plurality of amplifiers are cascode-connected to each other.
For example, the radio-frequency amplifier circuit disclosed in Patent Document 1 includes field-effect transistors TR1 and TR2. The gate of the field-effect transistor TR1 is connected to a radio-frequency input terminal. The source of the field-effect transistor TR1 is connected to a ground. The drain of the field-effect transistor TR1 and the source of the field-effect transistor TR2 are connected to each other. The drain of the field-effect transistor TR2 is connected to a drive voltage applying terminal via a choke coil. The drain of the field-effect transistor TR2 is connected to a radio-frequency output terminal via an output matching circuit.
A control signal is applied to the gate of each of the field-effect transistors TR1 and TR2.
With this configuration, a radio-frequency amplifier circuit in which field-effect transistors TR1 and TR2 are cascode-connected to each other is implemented.
In the configuration disclosed in Patent Document 1, the output matching circuit connected to the gate of the field-effect transistor TR2 on the side of which is closer to the radio-frequency output terminal is appropriately set so as to adjust the phase shift of a radio-frequency signal passing through the radio-frequency amplifier circuit. With this arrangement, the gain control for the radio-frequency amplifier circuit is stabilized.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-9564